'\"
'\" Generated from file 'traverse\&.man' by tcllib/doctools with format 'nroff'
'\"
.TH "fileutil_traverse" n 0\&.6 tcllib "file utilities"
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.SH NAME
fileutil_traverse \- Iterative directory traversal
.SH SYNOPSIS
package require \fBTcl  8\&.3\fR
.sp
package require \fBfileutil::traverse  ?0\&.6?\fR
.sp
package require \fBfileutil \fR
.sp
package require \fBcontrol \fR
.sp
\fB::fileutil::traverse\fR ?\fIobjectName\fR? \fIpath\fR ?\fIoption\fR \fIvalue\fR\&.\&.\&.?
.sp
\fB$traverser\fR \fBcommand\fR ?\fIarg arg \&.\&.\&.\fR?
.sp
\fB$traverser\fR \fBfiles\fR
.sp
\fB$traverser\fR \fBforeach\fR \fIfilevar\fR \fIscript\fR
.sp
\fB$traverser\fR \fBnext\fR \fIfilevar\fR
.sp
.BE
.SH DESCRIPTION
.PP
This package provides objects for the programmable traversal of
directory hierarchies\&.
The main command exported by the package is:
.TP
\fB::fileutil::traverse\fR ?\fIobjectName\fR? \fIpath\fR ?\fIoption\fR \fIvalue\fR\&.\&.\&.?
The command creates a new traversal object with an associated global
Tcl command whose name is \fIobjectName\fR\&. This command may be used
to invoke various operations on the traverser\&.
If the string \fB%AUTO%\fR is used as the \fIobjectName\fR then a
unique name will be generated by the package itself\&.
.sp
Regarding the recognized options see section \fBOPTIONS\fR\&. Note
that all these options can be set only during the creation of the
traversal object\&. Changing them later is not possible and causes
errors to be thrown if attempted\&.
.sp
The object command has the following general form:
.RS
.TP
\fB$traverser\fR \fBcommand\fR ?\fIarg arg \&.\&.\&.\fR?
\fICommand\fR and its \fIarg\fRuments determine the exact behavior of
the object\&.
.RE
.PP
The following commands are possible for traversal objects:
.TP
\fB$traverser\fR \fBfiles\fR
This method is the most highlevel one provided by traversal
objects\&. When invoked it returns a list containing the names of all
files and directories matching the current configuration of the
traverser\&.
.TP
\fB$traverser\fR \fBforeach\fR \fIfilevar\fR \fIscript\fR
The highlevel \fBfiles\fR method (see above) is based on this
mid-level method\&. When invoked it finds all files and directories
matching per the current configuration and executes the \fIscript\fR
for each path\&. The current path under consideration is stored in the
variable named by \fIfilevar\fR\&. Both variable and script live / are
executed in the context of the caller of the method\&. In the method
\fBfiles\fR the script simply saves the found paths into the list
to return\&.
.TP
\fB$traverser\fR \fBnext\fR \fIfilevar\fR
This is the lowest possible interface to the traverser, the core all
higher methods are built on\&. When invoked it returns a boolean value
indicating whether it found a path matching the current configuration
(\fBTrue\fR), or not (\fBFalse\fR)\&. If a path was found it is
stored into the variable named by \fIfilevar\fR, in the context of the
caller\&.
.sp
The \fBforeach\fR method simply calls this method in a loop
until it returned \fBFalse\fR\&. This method is exposed so that we are
also able to incrementally traverse a directory hierarchy in an
event-based manner\&.
.sp
Note that the traverser does follow symbolic links, except when
doing so would cause it to enter a link-cycle\&. In other words, the
command takes care to \fInot\fR lose itself in infinite loops upon
encountering circular link structures\&. Note that even links which are
not followed will still appear in the result\&.
.PP
.SH OPTIONS
.TP
\fB-prefilter\fR command_prefix
This callback is executed for directories\&. Its result determines if
the traverser recurses into the directory or not\&. The default is to
always recurse into all directories\&. The callback is invoked with a
single argument, the \fIabsolute\fR path of the directory, and has to
return a boolean value, \fBTrue\fR when the directory passes the
filter, and \fBFalse\fR if not\&.
.TP
\fB-filter\fR command_prefix
This callback is executed for all paths\&. Its result determines if the
current path is a valid result, and returned by \fBnext\fR\&. The
default is to accept all paths as valid\&. The callback is invoked with
a single argument, the \fIabsolute\fR path to check, and has to
return a boolean value, \fBTrue\fR when the path passes the filter,
and \fBFalse\fR if not\&.
.TP
\fB-errorcmd\fR command_prefix
This callback is executed for all paths the traverser has trouble
with\&. Like being unable to change into them, get their status,
etc\&. The default is to ignore any such problems\&. The callback is
invoked with a two arguments, the \fIabsolute\fR path for which the
error occured, and the error message\&. Errors thrown by the filter
callbacks are handled through this callback too\&. Errors thrown by the
error callback itself are not caught and ignored, but allowed to pass
to the caller, i\&.e\&. however invoked the \fBnext\fR\&. Any other
results from the callback are ignored\&.
.PP
.SH "WARNINGS AND INCOMPATIBILITIES"
.TP
\fB0\&.4\&.4\fR
In this version the traverser's broken system for handling symlinks
was replaced with one working correctly and properly enumerating all
the legal non-cyclic paths under a base directory\&.
.sp
While correct this means that certain pathological directory
hierarchies with cross-linked sym-links will now take about O(n**2)
time to enumerate whereas the original broken code managed O(n) due to
its brokenness\&.
.sp
A concrete example and extreme case is the "\fI/sys\fR"
hierarchy under Linux where some hundred devices exist under both
"\fI/sys/devices\fR" and "\fI/sys/class\fR" with the two sub-hierarchies
linking to the other, generating millions of legal paths to enumerate\&.
The structure, reduced to three devices, roughly looks like
.CS


	/sys/class/tty/tty0 --> \&.\&./\&.\&./dev/tty0
	/sys/class/tty/tty1 --> \&.\&./\&.\&./dev/tty1
	/sys/class/tty/tty2 --> \&.\&./\&.\&./dev/tty1

	/sys/dev/tty0/bus
	/sys/dev/tty0/subsystem --> \&.\&./\&.\&./class/tty
	/sys/dev/tty1/bus
	/sys/dev/tty1/subsystem --> \&.\&./\&.\&./class/tty
	/sys/dev/tty2/bus
	/sys/dev/tty2/subsystem --> \&.\&./\&.\&./class/tty

.CE
.sp
When having to handle such a pathological hierarchy it is
recommended to use the \fB-prefilter\fR option to prevent the
traverser from following symbolic links, like so:
.CS


    package require fileutil::traverse

    proc NoLinks {fileName} {
        if {[string equal [file type $fileName] link]} {
            return 0
        }
        return 1
    }

    fileutil::traverse T /sys/devices -prefilter NoLinks
    T foreach p {
        puts $p
    }
    T destroy

.CE
.PP
.SH "BUGS, IDEAS, FEEDBACK"
This document, and the package it describes, will undoubtedly contain
bugs and other problems\&.
Please report such in the category \fIfileutil\fR of the
\fITcllib Trackers\fR [http://core\&.tcl\&.tk/tcllib/reportlist]\&.
Please also report any ideas for enhancements you may have for either
package and/or documentation\&.
.PP
When proposing code changes, please provide \fIunified diffs\fR,
i\&.e the output of \fBdiff -u\fR\&.
.PP
Note further that \fIattachments\fR are strongly preferred over
inlined patches\&. Attachments can be made by going to the \fBEdit\fR
form of the ticket immediately after its creation, and then using the
left-most button in the secondary navigation bar\&.
.SH KEYWORDS
directory traversal, traversal
.SH CATEGORY
Programming tools
